The present invention relates to a new and improved apparatus for testing the responsiveness of an intrusion detector to environment-caused and detector-specific useful and spurious signals and for locating the electrical parameters which deviate from the nominal value.
Presently it is known that, for monitoring objects such as, for example, factories, administration buildings, stores, exhibition buildings, shopping centers, banks, open areas, parking areas, airports and so forth, systems are used which detect the intrusion of intruders and direct an intrusion alarm signal to the group of persons responsible for the protection of these objects such as, for instance, security forces or police. The monitoring systems contain a multitude of intrusion detectors which are distributed over the large-area object. These intrusion detectors are connected to a central station or a number of sub-central stations which, on response of the intrusion detector, generate the alarm and pass it on to the object protectors. The intrusion detectors are constructed as infrared detectors, ultrasonic detectors, microwave detectors, sonic detectors, vibration detectors, as well as capacitative detectors. These intrusion detectors commonly respond to environment-caused or detector-specific signals. Intrusion-specific signals such as those, for instance, due to the movement of persons, due to the noise of breaking glass, or due to mechanical action upon walls and objects, generate an electrical signal level in the intrusion detector. This electrical signal level in the intrusion detector totally or partially reaches the alarm threshold depending upon the distance of the intrusion detector from the event or happening. THe intention is that at least that intrusion detector will respond which is closest to the event or happening. An alarm is only generated if a predetermined threshold level is exceeded. The intrusion detectors also respond to spurious signals. Environment-caused spurious signals are, for instance, noises, air turbulences, temperature fluctuations and so forth. Detector-specific spurious signals are, for instance, sensor noise and so forth. When the spurious signals i.e. the environment-caused spurious signals or the detector-specific spurious signals, reach a certain level, the danger of false alarms will increase.
Furthermore, false alarms can occur when components of the intrusion detector deviate from their nominal operating values due to aging, intolerable environmental influences, such as for instance, condensation, vibrations, sabotage actions, and so forth. These false alarms can be a direct result of these deviations. Furthermore, environment-caused spurious signals which are normally suppressed may trigger false alarms due to a parameter deviation in certain components.
In U.S. Pat. No. 3,383,678, an intrusion detector for detecting movement is described which operates according to Doppler Principle. In this patent there is also described a function control of the electrical components of the intrusion detector. This function control is carried out in such a manner that a portion of the transmission power is coupled-out before the antenna and infed via a "motion simulator" at the output of the receiving antenna. The object of the "motion simulator" is to simulate the movement of an intruder and to thereby check the function of the electrical part of the intrusion detector during the presence of an intrusion signal. However, during this check on the operability of the intrusion detector, there can not be determined to what extent individual components of the intrusion detector have deviated from their nominal values. By means of this test there has only been determined the response of the intrusion detector to movement influences. The response of the intrusion detectors during disturbances thereby is not yet tested. The latter implies that the intrusion detector is prone to false alarms. It is noted as a further disadvantage that the check discribed hereinbefore does not permit a localization of the fault in the electrical circuit. The described check is a mere function check which can only be carried out during the operation of the intrusion detector.